This proposal is a renewal application for HL-45136. The longterm goal of the applicant is to elucidate the control of alveolar epithelial injury/repair and its anomolies that lead to lung fibrosis. In past award periods, the P.I. demonstrated that angiotensin II (ANGII) is a potent inducer of apoptosis in alveolar epithelial cells (AECs) and that de novo synthesis of ANGII by AECs, i.e. from its precursor angiotensinogen (ANGEN), is required for apoptosis in response to FasLigand, TNF-alpha, bleomycin (BLEO) or amiodarone (AMIO). In the most recent award period the P.I. has demonstrated that ANGEN gene transcription in AECs is induced by AP-1 family transcription factors acting at the core promoter and upstream sequences. Newer suggest this regulation also requires JNK and PARP-1. Additional recent preliminary studies suggest that the enzyme ACE-2, one of the peptidases that degrades ANGII, inhibits AEC apoptosis and lung fibrosis by a) limiting the accumulation of ANGII, and b) by producing from it the inhibitory peptide ANG1-7, which antagonizes the effect of ANGII. Moreover, mouse AECs in culture were found to express mas, the receptor for ANG1-7. The present proposal plans to extend these observations through four Specific Aims. In Aim 1, the molecular control of ANGEN gene expression by AECs will be studied further with a human ANGEN promoter-luciferase reporter, site-directed mutagenesis, mass spectrometry and CHIP assay. Aim 2 will use ACE-2 knockdown and overexpression strategies for manipulating ACE-2 in mice to elucidate its role in lung fibrogenesis. In Aim 3, the mouse AEC cell line MLE-12 will be used to elucidate the role(s) of ACE-2 in regulating autocrine production of ANGII and apoptosis, under both basal and stimulated conditions. Aim 4 will use oligonucleotide microarrays and proteomics to define subsets of ANG1-7- responsive genes and mas-dependent signaling mechanisms in cultured mouse AECs. Together, the proposed experiments will clarify our understanding of the local Angiotensin System in the alveolar epithelium and its regulation in lung injury and fibrogenesis. This information will ultimately be useful in the design of new therapeutic strategies for the treatment of fibrotic lung diseases.